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Slide 1
7
Memory
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Slide 2
Memory
Three Stages of Memory:
An Information-Processing View
• Information processing theories
– Brain and computer operations are similar
• Information-processing model
– Operations: input, storage, and retrieval
– Variety of control mechanisms at each point
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Information-Processing Theory
Slide 3
Sensory
information
STORAGE
economics literature
INPUT
RETRIEVAL
Information is
taken into brain
Information is used
as basis of behaviors
and interactions
culture science
religion
history
Information gets
processed, analyzed,
and stored until use
math
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Slide 4
Memory
Memory
• Information-processing model
– Information enters through sensory receptors
– Attention selects information to be entered
– Information encoded for next memory stage
– Some memory is saved, other information is
lost or discarded
• Stage theory of memory
– Assumes humans have 3-stage memory
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Slide 5
lasts less Discarded
than a
second,
interprets
stimulus
Stimuli
(input)
Sensory
Register
Discarded
Working
Memory
(Short-term
Memory)
Long-Term
Memory
(increasing
or
decreasing
availability)
Response
(output
or
reaction
behavior)
Control Processes
(selective attention, emotional regulation, strategic thinking)
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Slide 6
Memory
Stages of Memory
• Sensory register
– Holds image or experience until processing
– Can last up to 4 seconds; usually lasts less
• Short-term memory (STM)
– Usually attention transfers information from
sensory register to STM
– Usually information lasts less than one minute
unless control processes like rehearsal and
chunking are used
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Slide 7
Demonstration
Attend to the words in the green box as they flash
on the screen. When the last word disappears,
write down as many words as you can recall.
TABLE
SNOW
FOOT
DOG
SON
END
HAT
BUS
BREAD
DOOR
CAT
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Slide 8
Memory
Stages of Memory
– Rehearsal – mental repetition of information
• Humans have preference for transforming
information into acoustic codes or sounds
– Chunking – grouping information into bits
• Capacity limited to 7 items plus or minus 2
• Rare to hold between 5 and 9 items in STM
• STM functions
– Temporary storage of information
– Serves as working memory: space used for
retrieved memories from long-term memory
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Accuracy of recall for a single group of
three consonants declines rapidly when
subjects are prevented from rehearsing
by being asked to count backwards
Slide 9
Percent of accuracy of recall
100
80
60
40
20
0
0
3
6
9
12
Interval before recall in seconds
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15
18
Slide 10
Memory
Stages of Memory
Differences between LTM and STM
• Volume: vast amount
• Type of information
– Indexed and retrieved
– In terms of meaning
selectively by cues
or semantic codes
• Processing location
• Durability
– STM – frontal lobes
– Appears to be
of cortex
permanent,
– LTM – hippocampus
forgetting occurs
then transferred to
other brain areas
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Slide 11
Memory
Types of Long-Term Memory
• Procedural
– Memory for skills and procedures
(how to)
• Episodic
– Information about time and places
(when, where)
• Semantic
– Memory for meaning (importance)
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Slide 12
Memory
Long-Term Memory
• Long-term memory
– Storehouse for almost unlimited information
over long periods of time
– Easy to store procedural and semantic
memories, but stores episodic information
less well
– Semantic and episodic memories grouped
together as declarative memory
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Slide 13
Types of Long Term Memory
Declarative memory
Semantic memory
“I know what
a guitar is.”
Procedural memory
Episodic memory
“I remember buying
my first guitar.”
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“I remember how
to play a guitar.”
Slide 14
Memory
Organization in Long-Term Memory
• Organization eases retrieval process
– Grouped into categories
– Associative network: memories linked together
through experience
– Spreading activation model: representations of
concepts and their characteristics are activated
(ie: canary and bird)
• Closeness of association affects retrieval
time – distant associations take longer
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Slide 15
Example of Associative Links
Tiger
Cat
Animal
Skin
Dog
Breathes
Pat
Sparrow
Bird
Canary
Robin
Ostrich
Red
Orange
Feathers
Yellow
Sings
Green
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Slide 16
Memory
Retrieval of Long-Term Memories
• Frustration of unable to retrieve information
• Three ways to test retrieval
– Recall method: cues or hints used for recall
– Recognition method: select correct from
alternative information (ie: multiple choice)
– Relearning method: relearn previous learned
information
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Slide 17
Memory
Serial Learning
• Order of memorizing is as important as
items on the list
• Serial position effect – better recall of
items at beginning and end of lists
– Affected by timing or delay of recall
– Involves simultaneous use of STM and LTM
• Tip-of-the-tongue phenomenon
– Most recall occurs within a few minutes
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Slide 18
Effects of Recall Timing on Short-Term Memory
80
Tested immediately
Test delayed 20 seconds
Proportion correct
70
60
50
40
30
20
0
1
2
3
4
5
6
7
8
9
10
Position in original list
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11 12 13 14 15
16
Slide 19
Memory
Levels of Processing:
An Alternative to the Stage Model
• Two levels of memory processing
• Distinction between STM and LTM
– Matter of degree, not separate stages
– Differing levels of processing during
encoding process
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Slide 20
Memory
Levels of Processing:
An Alternative to the Stage Model
• Processing continuum
– Shallow level – processed briefly
– Deeper level – processed much deeper
involves greater elaboration (creating
more associations between new and
existing memories)
• An excellent way to improve memory
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Slide 21
Memory
Forgetting and Why It Occurs
• Decay theory
– Unused memories fade gradually over time
– Causes of forgetting
• fading memory traces over time
• Interference with retrieval
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Slide 22
Memory
Forgetting and Why It Occurs
• Interference theory
– Other memories interfere with retrieval
– Interference mostly from similar memories
• Types of interference
– Proactive – interference from prior learning
– Reactive – interference from later learning
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Slide 23
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Slide 24
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Slide 25
Memory
Forgetting and Why It Occurs
• Interfering with STM
– Overloading STM capacity or weakening/
blocking an item out of storage
• Interference with LTM
– Interference plays lesser role in disrupting
semantic memories than in episodic memories
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Slide 26
Memory
Reconstruction (Schema) Theory
• Schemas – associative networks of beliefs,
knowledge, and expectations
– During retrieval process, LTM information
recalled in distorted and incorrect manner that is
consistent with our schemas
• May occur because brain stores meaning
better than episodic details
• May result in false memory – recalling
something that never happened
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Slide 27
Memory
Motivated Forgetting
• Freud: some threatening information is
repressed – pushed into unconsciousness
• Emotional arousal improves memory in
some ways or has little effect on memory
– Mild levels of positive and negative arousal
appear to enhance memory
– Emotion-laden violence on TV programs
decreases recall of program advertisements
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Slide 28
Memory
Human Diversity: Cultural
Circumstances and Memory Skills
• Kearins – environmental demands and
culture may influence type of memory
used
– Aboriginals have better visual memory skills
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Slide 29
Memory
Biological Basis of Memory
• Synaptic theories of memory
– Physical change must occur in nervous system
– Engram: something remaining after learning
– Synaptic facilitation (Hebb) is biological basis
of learning and memory
• Individual experiences produce unique
patterns of neural activity causing structural
changes in synapses
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Slide 30
Memory
Biological Basis of Memory
• Synaptic theories of memory
– Classical conditioning of snails (Kandel)
• Amount of neurotransmitter in synapse
increased – synapse holds memory
• Drugs that interfere with protein synthesis
block memory formation
• Consolidation – fragile memories grow
more permanent over a few minutes
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Slide 31
Memory
Stages of Memory and the Brain
• STM and LTM differences in brain
– In role of synaptic changes: synapse changes
involved in LTM but not STM
– In brain structures involved
• Three stages of memory involve various
structures of brain as information is stored
and retrieved
– Allows memory recall with visual
images or auditory sensations
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Slide 32
Memory
Amnesia: Disorders of Memory
• Retrograde amnesia
– No memory of what happened immediately
before an accident or highly stressful event
• Little or no disruption in STM
• New long-term memories can be formed
• Usually memory loss does not last lifetime
• Stress of event disrupts consolidation and
retroactive interference blocks retrieval
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Slide 33
Memory
Amnesia: Disorders of Memory
• Anterograde amnesia
– Inability to store and retrieve new information
– Case of H.M. – epilepsy and neurosurgery
• Does not affect procedural memory abilities
but disrupts episodic memory formation
• Hippocampus involved in episodic memory
– Damage prevents formation of new longterm declarative memories
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Slide 34
Memory
Amnesia: Disorders of Memory
• Korsakoff’s syndrome
– Brain disorder from prolonged loss of vitamin
thiamine as in diet of chronic alcoholics
– Extreme degree of memory loss
– Often engage in confabulation – cannot
remember ending to a statement so make it up;
an exaggerated version of normal reconstruction
distortion
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Slide 35
Memory
Inaccurate Recall Due to Biased
Questioning
• Research on eyewitness information
– Can be potent source of distortion
• Interviewer questions can contain cues that
influence retrieval
• Reconstruction theory of forgetting – people
remember something that did not occur
because it seemed consistent with the event
• Perceived expertise of interviewer may bias
informational response
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Slide 36
Memory
Inaccurate Eyewitness Recall
• Eyewitness testimony frequently inaccurate
– Children, adolescents are particularly
suggestible when interviewed by adults
• Sometimes describe what never happened
• Neutral questions get best results
• Eyewitnesses who look but do not see
– Some things processed in shallow ways due to
inattentiveness or lack of importance attached
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Slide 37
Memory
Stereotypes and Eyewitness Testimony
• Allport: memories distorted by prejudices
– Research in US – common African American
names more stereotyped with criminality when
memories fit personal schemas of prejudice
• Inaccurate recall due to characteristics of the
eyewitness
– Being tired, upset, intoxicated may effect recall
– Drunk eyewitness: visual recall may be accurate
in some circumstances
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Slide 38
Memory
Recall of Repressed Memories of
Sexual and Physical Abuse
• Most compelling testimony is from victims
– Many cases of repressed memories when adult
was abused as child now in media
• Dilemma - hard to know what is accurate
• Many traumatic childhood memories
discovered in psychotherapy may be false
memories
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Slide 39
Memory
Hypnosis and Eyewitness Testimony
• Hypnotizing witnesses to crimes is
controversial
– Hypnotic age regression: hypnotized person
goes back in time to earlier age – relives event
and recalls forgotten experiences
• May be heightened imagination more than
accurate relived memories
– Hypnotized witnesses to recent crimes may
have more accurate recall
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Slide 40
Memory
Improving the Accuracy of
Eyewitnesses’ Testimony
• Thousands of experiments in research have
raised concerns but little has been done
– DNA saved innocent persons on death row
convicted on eyewitness testimony
– U.S. Dept. of Justice made recommendations
in 1999 about use of eyewitness testimony
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Slide 41
Memory
Eyewitness Testimony
• Recommendations
– Establish good rapport
– Ask open-ended questions
– Use fillers in lineup fitting witness description
– Place only one suspect in identification lineup
– Unbiased instructions to eyewitnesses before
viewing photos and lineups
– Avoid giving feedback to eyewitnesses after
identification of photo or person in lineup
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Slide 42
Memory
7
The End
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved